In the past, many spacecrafts carrying a solar cell panel have been lofted into space. As spacecrafts become more sophisticated in functionality, solar cell panels which can supply high power to spacecrafts are needed. The need to raise the output voltages of solar cell panels has therefore arisen from this necessity for the supply of high power. Since the potential difference between solar cells in a solar cell panel becomes large with increase in the output voltage of the solar cell panel, an electric discharge which originates from power generated by the solar cells which is an energy source can easily occur between the solar cells.
A prior art solar cell panel in which an insulating material, such as an RTV adhesive, is filled into the gap between solar cells in the solar cell panel and is used as an insulating barrier is known as a measure for preventing an electric discharge from occurring between the solar cells (refer to patent reference 1, for example).                [Patent Reference 1] Japanese patent application publication No. 11-274,542 (see FIGS. 11 and 18)        
The prior art solar cell panel in which an insulating material, such as an RTV adhesive, is placed in the gap between solar cells in the solar cell panel and is used as an insulating barrier has the following problems. The first problem is that the prior art solar cell panel increases in weight by only the weight of the adhesive which is used as the insulating barrier. The second problem is that the prior art solar cell panel increases in cost because of increase in the material cost of the adhesive which is used as the insulating barrier, the cost of installing the insulating barrier, increase in the cost of launching a rocket, and so on.
According to patent reference 1, since any two adjacent solar cell assembly series are so connected as to have different gradient directions in their potentials with respect to a folded connection point therebetween, any two adjacent solar cells in any two adjacent solar cell assembly series have a minimum potential difference of 0 volts at their lowermost ends and a maximum potential difference of 2V volts at their uppermost ends when each solar cell assembly series has a potential difference of V volts. The uppermost ends of any two adjacent solar cell assembly series having the maximum potential difference are at increased risk of causing electrostatic discharges.
The smaller potential difference solar cells have, the lower risk of causing electric discharges between the solar cells. When there is no insulating barrier between any solar cells, an adequate margin of safety can be provided against electric discharges if the voltages of solar cells are reduced to ½ or less of original ones, as compared with a case where an insulating barrier is provided between any solar cells (refer to paragraph number (0049) of patent reference 1). Therefore, implementation of an arrangement of solar cells which can reduce the potential difference between any two adjacent solar cells is effective in preventing electric discharges from occurring between any solar cells.
The present invention is made in order to solve the above-mentioned problems, and it is therefore an object of the present invention to provide a solar cell panel that can prevent electric discharges from occurring between any solar cells without installing an insulating barrier in the gap between any solar cells.
It is another object of the present invention to provide a solar cell panel in which the potential difference between any two adjacent solar cells is reduced to less than 2V volts in the prior art even when installing an insulating barrier into the gap between any two solar cells, thereby providing a more adequate margin of safety against electric discharges between solar cells as compared with prior art solar cell panels.